Smelting lead ores in the scotch hearth



Nov. 26, 1940- c. e. HERSHEY EI'AL.

SMELTING LEAD ORES IN THE SCOTCH HEARTH Filed July 13, 1939 li ailu w ma NE w Mm IR R c LUTHER J. BUCK Patented Nov. 26, 1940- UNITED STATES PATENT OFFICE SMELTING LEAD ORES IN THE SCOTCH HEARTH Carl G. Hershey and Luther J. Buck, Alton, Ill., assignors to American smelting and Refining Company, New Yo N. Y., a corporation of New Jersey Application July 13, 1939, Serial No. 284,180

5 Claims.

This invention relates to the smelting of lead ores and provides certain improvements in Scotch hearth practise.

The reduction of lead ores by the roast reac- 5 tion process is, of course, well known and an excellent summary of the development of the process, as well as a description of a typical modern ore hearth, appears in the article by L. J. Buck in Transactions of the A. I. M. E., volume 121, Metallurgy of Lead and Zinc (1936).

As ordinarily practised, the ore hearth is provided with a water-cooled back wall and to effect the roast reaction and reduction of the lead, air is supplied to the charge upon the hearth through tuyeres in the back wall positioned immediately below the bottom of the chamber in which the cooling water is circulated.

It has now been found that improved results are obtained by preheating the air of the blast before it is introduced into the charge upon the hearth, such preheating being appropriately accomplished by utilizing the blast to cool the hearth back wall.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, and the manner in which it may be carried out, may be better understood by referring to the following description taken in connection with the accompanying drawing forming a part thereof, in which Fig. 1 is a rear view of a Scotch hearth for practising the invention. a portion of the jacket air header being broken away to show the cooling fins for the back wall of the hearth, and

Fig. 2 is a cross-section of the hearth shown in Fig. 1 taken along the line 2-2 thereof.

Like reference characters denote like parts in the several figures of the drawing.

Referring to the drawing more in detail, the furnace is shown with a blast header l0, jacket air header l2, and steel back wall It to which are welded cooling has It. A baiiie It extends from the jacket 20 to the tuyeres 22 along the bottom edges of the cooling fins I but above the tuyeres 22 and tuyere cleanouts 24. To the front of the furnace are basin 2' and apron as over which is hood ll. The level of lead in the basin is indicated at 22 while 24 represents the overlying charge.

In operating the hearth, air from the blast header ll is delivered to the jacket air header I2 and passes downwardly about the ilns it thereby cooling the back wall It and itself becoming heated.

Thebafllelecausestheairtopass around the tuyeres 22, thence through them and into the charge 34. As the roast reaction proceeds and the lead compounds in the charge are reduced to metallic lead, the liquid metal enters the basin 26 and is tapped from time to 5 time.

Among the advantages attending the use of the invention are: the preheating of the air reduces the amount of fue1 required in the charge and experience to date indicates that the extraction of lead is increased accompanied by a decrease in the amount of fume and slag produced; air cooling of the hearth avoids any necessity for a water system and its maintenance; and expenses incident to the cleaning and replacement of water jackets, by reason of sediment and scale formation, is eliminated.

It will be understood that in the appended claims, the term air is used in its broad sense as embracing not only the normal atmosphere but also mixtures of the same and diluent gases, unless otherwise specified.

What is claimed is= 1. In reducing lead ores by the roast reaction process in an ore hearth having a back wall, the 25 improvement which consists in utilizing the air blast to cool the back wall of the hearth prior to introducing the air into the charge upon the hearth.

2. In reducing lead ores by the roast reaction process employing a blast of undiluted air, that improvement which consists in preheating said blast prior to supplying it to the charge.

3. The process for treating lead ores in a Scotch hearth which comprises subjecting same 35 to the roast reaction process, and preheating the air introduced into the charge to support combustion by previously utilizing said air as the cooling medium in cooling the back wall of the hearth.

4. An ore hearth for treating lead ores by the roast reaction process in which the back of the back wall of the hearth is provided with fins for dissipating heat from, and thereby cooling. said back wall, and means for conducting air 45 between said fins and thence to said hearth.

5. The combination with an ore hearth for treating lead ores by the roast reaction process having means for delivering an air blast to the hearth, a basin, apron and hood. of an air- 5 cooled back wall for said hearth. and means for cooling said back wall with the air blast thereby preheating the latter prior to delivering same to 

